The present invention relates to the field of connection constructions for electronic components, and more specifically relates to such a connection construction which is particularly suitable for handling high speed signals.
In FIG. 7 of the accompanying drawings there is illustrated a prior art type of connecting structure for an electronic component. In this structure, electronic components designated as 3 and 5 are mounted to the upper and the lower surfaces in the figure of an electronic circuit board 1, and external connection terminals 7 (input and output terminals) are mounted to one edge of said circuit board 1, with said circuit board 1 being fixed at an intermediate position inside a synthetic resin case 9, and with said external connection terminals 7 projecting downwards through the bottom in the figure of said case 9.
In such a structure for providing connection for an electronic component, if as is per se known and as is shown in more detailed perspective view in FIG. 8 a ground plane 13 is formed on the lower side in the figure of the circuit board 1, so as to oppose a circuit pattern 11 formed (by printing or the like) on the upper side in the figure of said circuit board 1 and connected to the external connection terminals 7 and to the electronic components 3 and 5 (which are omitted from this figure) so as electrically to connect these elements together, then the circuit pattern 11 will act as a conductive strip having a certain characteristic impedance, and the degradation, such as distortion and/or attenuation, of a super high speed signal which is being transmitted between said electronic components 3 and 5 and said external connection terminals 7 will not develop.
However, the parts of the external connection terminals 7 which are connected to external circuits do not form such a transmission line with a certain characteristic impedance, and neither do the parts of said external connection terminals 7 which lead to said connection parts, i.e. the down legs as seen in FIGS. 7 and 8. Accordingly, the risk of mismatching exists in such a part of the construction, and there is likely to be degradation of the super high speed signal.
In particular, if the electronic components in the case 9 constitute a programmable variable delay line which incorporates, as electronic component parts, a super high speed electromagnetic delay line and a high speed IC such as an ECL for digitally switching over the delay time of this super high speed electromagnetic delay line, then it is difficult to drastically reduce the dimensions of the super high speed electromagnetic delay line, with the result that the overall size cannot be satisfactorily reduced, and the degree of mismatching at the external connection terminals 7 may not be at all negligible, due to the inevitably extended length of said external connection terminals 7.